The general goals of the proposed research are an enhanced understanding of the neuromotor basis of stuttering and the development of improved forms of speech therapy for persons who stutter. The problem of stuttering can reasonably be viewed as a motor disorder. From this perspective, speech disfluency is likely to be the result of the interaction of several forms of neural input to pattern generating circuitry within the motor systems of the brain. Such input involves, for example, systems in the brain that mediate phonetic pattern selection (i.e. the particular sounds we produce), emotional response, and speech rate or how fast we speak. Given the complexity of this overall system, it is logical that we develop improved methods for evaluating speech pattern generating function while controlling for these different sources of input. This approach is taken in the present research through analyses of orofacial movements and voice acoustics. A central issue in the study of pattern generating function for speech concerns how different muscle systems (e.g., tongue and jaw) are controlled and coordinated. This general issue will be studied through analysis of orofacial movements and voice acoustics in individuals with a history of stuttering and a group of normal speakers. An electromagnetic system will be used to record displacements of the upper lip, lower lip, jaw, and tongue while subjects repeat a limited set of speech utterances at varying rates and vocal intensities. A wide range of clinical-behavioral measures of speech performance will be obtained in stutterer subjects. A general hypothesis underlying much of the work is that there are subgroups of individuals whose pattern generating function for speech reflects different motor strategies, and these strategies have varying levels of inherent stability or propensity for disfluency. This and related hypotheses will be addressed in relation to investigations concerning (1) the association of orofacial and voice acoustic measures in normal speakers, (2) the association of speech motor output to clinical-behavioral measures of speech performance in persons who stutter, (3) the effects of speech therapy on speech motor output, (4) the existence of speech motor subgroups, and (5) the temporal-spatial characteristics of orofacial movements and voice acoustics during disfluency. Work on these various problems should lead to an improved basis for clinical categorization of persons who stutter, better understanding of the changes in motor performance associated with speech therapy, and a broad data base for computational modeling of speech motor control and simulation of the mechanisms of speech disfluency.